In recent years, highly advanced illumination systems are being developed to allow a user to obtain a desired ambiance for a particular room or space. In these illumination systems so called scene setting is employed, where one or more sets of light sources are controlled simultaneously, contrary to traditional control of individual light sources with respect to e.g. switching on/off, dimming, and color setting. For these scene setting applications, intuitive user interaction is an important success factor. Providing a user with information related to the light sources, like localized identification of the individual light sources, their capacities, and their current setting, is key for enabling an intuitive interaction.
To provide such information to the user, techniques based on coded light, CL, have been proposed. CL is based on embedding data into the light output of the light sources. The light output of a light source is typically modulated in response to a repeating data signal, which may contain identifier codes, e.g. identifying codes for identifying the light source or a group of light sources to which the light source belongs. The modulation typically occurs at a frequency that is sufficiently high to be imperceptible by humans. Simultaneous detection of light contributions from multiple light sources is possible by modulating each light source in a unique fashion. There exist various methods, continuous and binary, allowing both synchronous and asynchronous detection of a (theoretically) unlimited number of light sources.
It has been previously shown how CL technology can be used for commissioning of lighting systems, e.g. by pointing to the individual light sources and reading out the identifier codes.
The embedded data, e.g. identifier codes, in the light output of the light sources may be detected by an optical receiver which may, be implemented in e.g. a remote control for controlling the lamp or included in another unit such as a switch or a sensor device. This has a drawback that only embedded data present at single positions can be detected. In contrast it is desirable to characterize the whole two dimensional (2D) scene in real time in terms of identifier codes being present, and distinguishing the identifier codes of the different light sources in the light scene.
Camera sensors have been proposed that can determine embedded data present at multiple positions within an image of a scene. However, a drawback of the previous techniques employing camera sensors is that the time between subsequent image acquisitions must generally be equal to, or shorter than, the duration of a single bit within the embedded code. Consecutive bits of the embedded code are then detected by analyzing results obtained in consecutive acquisitions of the camera. This requires the use of advanced and therefore expensive cameras capable of providing a high acquisition rate. Conventional low-cost camera sensors typically have too low of an acquisition rate to be useful for detecting embedded data being invisible to the human eye, i.e. high frequency CL.
Thus, there is a need in the art for a technique for detecting CL embedded into a light output of light sources that addresses at least some of the above mentioned problems.